Physics QCAA 2023

Normal Force

Normal Force

the perpendicular contact force exerted by a surface on another object

Uniform Circular Motion

the movement of an object at a constant speed around a circle with a fixed radius, where the force acts perpendicular to the velocity of the object

Average speed

total distance/total time

Period

Time required to complete one revolution. T=1/f

Centripetal acceleration

The acceleration of a body traversing a circular path

Centripetal Force

a force that acts on a body moving in a circular path and is directed away from the centre (perpendicular from the velocity tangent).

Newton's Law of Gravitation

The force between two point masses is directly proportional to the product of the masses and inversely proportional to the square of the separation between them

Gravitational Fields

The region of space surrounding a body in which another body experiences a force of gravitational attraction.

Kepler's First Law of Planetary Motion

The first law states that all planets travel around the Sun in elliptical orbits with the Sun at one focus.

Kepler's Second Law of Planetary Motion

The second law states that a line from any planet to the Sun sweeps out equal areas in equal lengths of time.

Kepler's Third Law of Planetary Motion

The third law states that the squares of the sidereal periods of the planets are directly proportional to the cubes of their mean distance from the Sun.

deriving Kepler's Third law

Using the relationship between Newton's Law of Universal Gravitation and uniform circular motion.

Coulomb's Law

Coulomb's Law describes the force exerted by electrostatically charged objects on other electrostatically charged objects. It states that like electric charges repel and opposite electric charges attract, with a force proportional to the product of the electric charges and inversely proportional to the square of the distance between them,

Electric Field

The region of space surrounding an electrically charged particle or object in which another electrically charged particle or object experiences a force.

Electric Field Strength

The intensity of an electric field at a particular location (measured in N/C)

Electric Potential Energy

The capacity of electric charge carriers to do work is due to their position in an electric circuit.

Magnetic Field

The region of space surrounding a magnet, electric current or moving electrically charged particle in which another magnet, electric current or moving electrically charged particle experiences a magnetic force (SI unit; T).

Magnetic Flux

A measurement of the total magnetic field that passes through a given area (symbol, 𝜙; SI unit, Wb)The angle is between the perpendicular to the loop and the field.

Magnetic Flux Density

The strength of a magnetic field per unit area (symbol, 𝐵; SI unit, Wb/m² or T).

Electromagnetic Induction

The production of a voltage or EMF across an electrical conductor due to its dynamic interaction with a magnetic field.

EMF (Electromotive Force)

A difference in potential that tends to give rise to an electric current, (measured in V). EMF= -n(∆𝜙/∆t)

Faraday's Law

A law stating that change in magnetic flux induces an electromotive force in a circuit, which is directly proportional to the rate of change of the magnetic flux. This creates a current. EMF= -n(∆𝜙/∆t)

Lenz's Law

A law stating that the direction of induced current will be such that the change in magnetic flux is opposed by the induced magnetic field.

How can EMF be induced by moving a conductor across a magnetic field?

Moving a conductor in a uniform magnetic field results in an induced emf across the conductor. As the conductor moves, there is a change in magnetic flux, due to the change in area of the conductor that is exposed to the magnetic field lines.

Electromagnetic Radiation

Electromagnetic radiation is energy made up of synchronised oscillating electric and magnetic fields propagate at the speed of light in a vacuum.

Frame of Reference

The abstract coordinate system that defines location of the observer

Inertial Frame of Reference

A non-accelerating frame of reference in which Newton's laws of motion hold.

Muon Paradox

The half-life of a muon is 2.2 microseconds and so even moving at 0.994 c they would only expect to travel about 660 m before half of them decayed. Muons formed at, say 12000 m would take 40 <μs or about 20 half-lives to reach the ground. This would mean that only 1/220 of the original number would be detected. The fact that the proportion is much higher than this means that the muons are living longer. At 0.994c the formula for time dilation gives the half-life for the muons to be 20 μs. This means that at 0.994c the proportion reaching the ground should be 0.25. This means that the number of muons per second detected at the ground is much greater than expected.

Postulates of Special Relativity

1. The laws of nature are the same for everyone.

2. The speed of light is the same for everyone.

Simultaneity

simultaneity is relative to a frame of axis. Two events are simultaneous in a given system of reference, if they occur at the same time, as measured by clocks that have been synchronized using light signals.

Time dialation

the difference of elapsed time between two events as measured by observers moving relative to each other.

Proper Time Interval

The time interval measured in the frame of reference in which the object is at rest.

Relativistic Time Interval

The time interval measured in the frame of reference in which the object is in motion.

Length Contraction

An observer at rest relative to a moving object would observe the moving object to be shorter along the dimension of motion.

Rest Mass

The mass of an object measured in the frame of reference in which the object is at rest.

Threshold Frequency

The minimum frequency of a photon is required to eject an electron from a surface.

Planck's Constant

defines the quantum nature of energy and relates the energy of a photon to its frequency

Work Function

The minimum energy required to eject an electron from a solid.

mass-energy equivalence

E=mc^2

Young's double split experiment

shows the constructive and destructive interference of waves that occur as light passes through parallel slits, resulting in minima (dark fringes) and maxima (bright fringes) of intensity

Light

an electromagnetic wave produced by an oscillating electric charge that produces mutually perpendicular oscillating electric fields and magnetic fields

Black Body Radiation

A black body is a body that absorbs all electromagnetic radiation, meaning it is in constant thermal equilibrium with its environment, which emits thermal electromagnetic radiation

Photon

A particle of electromagnetic radiation with no mass that carries a quantum of energy

Back body radiation is quantised?

The radiation emitted by a black body from the conversion of thermal energy, and which has a characteristic frequency distribution that depends on the temperature. Provides evidence that electromagnetic radiation is quantised as it does not reflect light, so it is an ideal emitter for EM radiation.

Rutherford Model

Concluded that the atom is mostly empty space, most of the mass & all of the charge of the atom was highly concentrated in the nucleus. Limitations: The failure to account for the stability of the atom, and the failure to account for emission lines in the hydrogen spectrum.

Bohr model of the atom and how it addresses the limitations of Rutherford's model

The Bohr model of the atom demonstrates that electrons exist in discrete energy levels, ultimately addressing Rutherford's model - that was limited in that it did not take into account the stability of the atom. Bohr also described that electrons can jump between energy levels, describing the emission spectrum.

Explain how the Bohr model of the hydrogen atom integrates light quanta and atomic energy states to explain the specific wavelengths in the hydrogen line spectrum

Bohr explained that electrons can move between the said discrete level by an addition of energy, as the electron moves back to its ground state it emits a photon, emitting a specific wavelength of radiation, drawing a line that corresponds to the hydrogen line spectrum.

Wave-particle duality

The concept that light as well as many subatomic particles have the properties of both particles and waves

Phenomena that explains light as a wave

Polarisation, diffraction and refraction

Phenomena that explains light as a particle

Photoelectric effect and the Compton effect (light having momentum)

Photoelectric Effect

Proves light acts like a particle because electrons are only emitted when light reaches the threshold frequency, rather than the intensity or brightness of light. This proves light energy is quantized.

Elementary Particle

a particle whose substructure is unknown

Anti particle

a particle with the same mass and opposite charge and/or spin to a corresponding particle, for example positron and electron

Types of Quarks

up, down, charm, strange, top, bottom

Baryon

Any hadron made with a combination of three quarks, where the colour charge adds to white

Meson

Any unstable and small nuclear particle that consists of a quark and an anti-quark where the colour charge is white

Types of Leptons

electron, muon, tau, electron neutrino, muon neutrino, tau neutrino

Types of Gauge bosons

gluon, photon, Z boson, W boson

Gauge boson

The exchange particles that transmit the four fundamental interactions between particles.